A washing cycle of laundry as performed by a laundry washing appliance generally comprises two phases: a washing phase and a rinse phase.
A wash program o process comprises one or more washing cycles and is possibly terminated by a final spinning phase. Additional spinning steps might be present between consecutive rinsing steps during the rinsing phase.
The washing phase represents the portion of each washing cycle during which water is supplied into the appliance possibly together with the detergent to form a washing liquor (wetting step), the washing liquor is possibly heated (heating step), the laundry to be washed is subjected to tumbling of the drum in order to repeatedly expose it to mechanical action and to the washing liquor, so that dirt is removed from the laundry and stabilized in the washing liquor (tumbling step) and finally the washing liquor in which dirt is stabilized, is drained from the washing chamber (draining step).
The key parameters involved in each washing phase are: temperature, amount of water, mechanical action, detergent type/amount and duration. In order to provide best results in washing performances vs. water and energy consumption, one or more of these parameters are generally optimized.
The rinsing phase aims to remove the residuals of dirt and detergent coming from the washing phase. In many appliances, the rinsing phase is performed stepwise, e.g. generally two or three rinsing steps are performed. Each step is commonly characterized by a defined amount of water, duration, and mechanical action.
In current laundry washing appliances, the duration of each washing phase and the timing between its subsequent phases or steps are preset by the selection of a washing program and other possible parameters without taking into account the effective water and/or laundry conditions. In other words, each next phase or step starts independent of the completion degree of the previous one. By way of an example, each washing phase of a wash program has usually a predefined duration which is fixed and dependent on the specific wash program chosen by the user.
The expression “predefined duration of a washing phase” is used to identify the duration preset by the choice of a specific wash program.
Applicant has realized that the effectiveness of the washing phase depends on the time that the laundry is exposed to the fully dissolved detergent into the washing liquor at the most appropriate temperature.
Furthermore, Applicant has noted that the time required to reach a full dissolution condition varies from detergent type to detergent type.
Many types of detergents to be used in laundry washing appliances are available nowadays.
The detergents can be classified into different kinds, depending on their physical state: there are detergents in powder form and detergents in liquid or gel form. Furthermore, the above detergent kinds can be found on the marked in conventional form or pre-dosed.
Throughout the present description, the expression “detergent in conventional form” is used to refer to a detergent which can be poured or introduced loose into the washing machine drawer in a quantity which can be freely decided by the user. Throughout the present description, the expression “pre-dosed detergent” is used to refer to a detergent which the user introduces directly into the drum in a pre-established quantity. The pre-dosed detergent can be in liquid, gel or powder form (the latter possibly pressed).
Pre-dosed detergents—especially pre-dosed detergents in liquid or gel form, but in some cases, also pre-dosed detergents in powder form—are conventionally encapsulated, namely enveloped in a plastic membrane which dissolves in water. Applicant has noticed that encapsulated detergents require a longer time before a condition of full dissolution into water is reached, compared to the other detergent types since the plastic membrane has to dissolve first, before dissolution of the detergent in water can start.
Moreover, the real dissolution time depends also on the specific loading conditions which could affect the exposure of the plastic membrane to water. By way of an example, the encapsulated detergent should be preferably placed on the bottom of the drum, before the laundry is loaded.
If the user does not follow the above loading sequence, the dissolution of the plastic membrane could take longer than expected so that the detergent would reach its dissolved state only towards the end of the washing phase.
This could lead to a reduced washing effectiveness since less time would be available for the dissolved detergent to act on the laundry during the washing phase.
This problem could arise also if the correct loading sequence is followed by the user. In fact, it could happen that the movement of the laundry inside of the drum pushes the encapsulated detergent towards the top of the laundry or the door gasket. In these positions, the encapsulated detergent does not get in contact with enough water in order to undergo a rapid dissolution.
The above considered, Applicant has realized that, a deeper correlation between the duration of the washing phase and the water and/or laundry conditions could lead to performance improvements and has focused its attention to the lack of coordination between detergent dissolution and the duration of the washing phase in current washing appliances.
Applicant has considered that setting a very long washing phase duration corresponding to the feasible longest detergent dissolution would imply, in most cases, an unnecessary extension of the overall wash program duration which could make the user believe that a deficiency is present in the washing apparatus itself, which is, in his/her opinion, not performing properly.
Applicant has thus understood that a modification in the laundry washing appliance has to be made in order to establish a tuning between detergent dissolution and the washing phase so as to link the duration of the washing phase to the real dissolution level of the detergent, thereby optimizing the washing performances while keeping short the overall washing cycle duration.